Movies not showing in Apple TV app

Media Sharing - Home Sharing turned on in System Preferences for the Mac and is Home Sharing turned on on the ATV and both devices on the same network.

Use Home Sharing to share media from a computer to other devices - Apple Support

Only your purchased/rented iTunes Store movies will show up in the TV app library on Apple TV box. Home Sharing on the Apple TV box is done through the Computers app.

The Apple TV app on smart TVs and third party streaming devices does not support Home Sharing.

Make sure your firewall is off under your Security & Privacy settings.....Also make sure Home sharing is on for both ATV and your computer.